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INFORMATION SHEET ORDER NO.R5-2004-0028 19 INFORMATION SHEET ORDER NO.R5-2004-0028 20
<br /> CITY OF MANTECA,CITY OF LATHROP AND DUTRA FARMS CITY OF MANTECA,CITY OF LATHROP AND DUTRA FARMS
<br /> WASTEWATER QUALITY CONTROL FACILITY WASTEWATER QUALITY CONTROL FACILITY
<br /> SAN JOAQUIN COUNTY SAN JOAQUIN COUNTY
<br /> hardness under design flow conditions(see Figure 1). The minimum flow at Vernalis is approximately DHS must revise the current total THMs MCL in Title 22 CCR to be as low or lower than the USEPA
<br /> 1000 cfs which is the flow that the U.S.Bureau of Reclamation maintains at Vernalis to meet the 1995 MCL. Total Trihalomethanes(THMs)include bromoform,bromodichloromethane,chloroform,and
<br /> Water Quality Control Plan salinity objective of 1000 umhos/cm. Hardness data was then evaluated in dibromochloromethane. Chloroform does not have promulgated CTR criteria. The State Board,in
<br /> the range of 800 to 1,200 cfs. The receiving water hardness generally ranged from 150 to 250 mg/1 as WQO No 2003-0002,stated that the Drinking Water Standard primary MCL for Total THMs of 80
<br /> CaCO3 with the lowest observed receiving water hardness under these conditions being 108 mg/I ug/l could be applied to address chloroform in the discharge regulated in that Order. In addition,the
<br /> CaCO3. At a hardness of 108 mg/l,the chronic criterion,or criterion continuous concentration(CCC), Cal/EPA Office of Environmental Health Hazard Assessment(OEHHA)has published the Toxicity
<br /> for copper is 9.6 ug/l. Criteria Database,which contains cancer potency factors for chemicals,including chloroform,that
<br /> have been used as a basis for regulatory actions by the boards,departments and offices within
<br /> Effluent hardness values ranged from 170 mg/1 to 190 mg/1 during the period from March 2002 to Cal/EPA. This cancer potency factor is equivalent to a concentration in drinking water of 1.1 ug/l
<br /> December 2002. Because no dilution is allowed for effluent limitations based on acute criteria,the (ppb)at the 1-in-a-million cancer risk level with the consumption of the drinking water over a 70-year
<br /> minimum effluent hardness value of 170 mg/1 was used for calculating effluent limitations. Using the lifetime. This risk level is consistent with that used by the Department of Health Services(DHS)to set
<br /> minimum effluent hardness,the acute criterion,or criterion maximum concentration(CMC),for de minimis risks from involuntary exposure to carcinogens in drinking water in developing MCLS and
<br /> copper is 22.2 ug/l as dissolved,based on the SIP. However,the hardness dependent SIP criterion Action Levels and by OEHHA to set negligible cancer risks in developing Public Health Goals for
<br /> exceeds the Basin Plan site-specific objective of 10 ug/1 as dissolved. Therefore,the copper effluent drinking water. The one-in-a-million cancer risk level is also mandated by USEPA in applying human
<br /> limits were calculated using a CMC of 10 ug/1 as dissolved. Effluent limitations,which are expressed health protective criteria contained in the National Toxics Rule and the California Toxics Rule to
<br /> as total recoverable,are somewhat higher after the application of a 0.96 translator.There have been no priority toxic pollutants in California surface waters.
<br /> approved studies by the Discharger to evaluate discharge-specific metal translators for copper;
<br /> therefore,the default USEPA translators within the CTR were used in the calculation of the final MUN is a designated beneficial use of the receiving water. However,there are no known drinking
<br /> effluent limitations. water intakes on the San Joaquin River within several miles downstream of the discharge,and
<br /> chloroform is a non-conservative pollutant. Therefore,to protect the MUN use of the receiving waters,
<br /> The final effluent limitations were calculated using a steady-state model method described in Section the Regional Board finds that,in this specific circumstance,application of the USEPA MCL for total
<br /> 1.4 of the SIP. Section 5.4.4 of the TSD was utilized to determine the monthly average limit for THMs for the effluent is appropriate,as long as the receiving water does not exceed the OEHHA
<br /> arsenic. Water quality-based effluent limitations are included in this Order based on the Basin Plan cancer potency factor's equivalent receiving water concentration at a reasonable distance from the
<br /> chemical constituents objective. The data are included in Table 9 and the effluent limitation outfall(e.g.,before reaching the drinking water intakes). Effluent samples collected from January
<br /> calculations in Table 11. 2002 through December 2002 indicated that THMs were present with a maximum concentration of 17
<br /> ug/1 and an average concentration of 10 ug/1. Chloroform samples collected over the same period
<br /> 11.2 Human Carcinogens contained a maximum concentration of 12 ug/1 and an average concentration of 8 ug/l. Considering
<br /> the available dilution based on the harmonic mean flow of the San Joaquin River,the discharge does
<br /> There were five(5)human carcinogenic compounds present in the WQCF effluent. As summarized in not have a reasonable potential to cause or contribute to an in-stream excursion above the water quality
<br /> Table 10,dibromochloromethane,bromodichloromethane,2,4,6-trichlorophenol,and bis(2- objective for MUN use by causing an exceedance of the USEPA primary MCL for total THMs or the
<br /> ethylhexyl)phthalate were determined to present reasonable potential to exceed a one-in-a-million chloroform OEHHA cancer potency factor's equivalent receiving water concentration. Therefore,
<br /> incremental human cancer risk criteria for water and/or organism consumption. Chloroform does not effluent limitations for total THMs and chloroform are not included in this Order.
<br /> show reasonable potential to exceed the primary MCL. None of these constituents were detected in the
<br /> receiving water. 11.2.2 Effluent Limitations for Human Carcinogenic Priority Pollutants
<br /> 11.2.1 Total Trihalomethanes and Chloroform The effluent limitation calculation procedures in Section 1.4 of the SIP allow for the granting of a
<br /> dilution credit which,in this case,is 222-fold based on the harmonic mean flow of the San Joaquin
<br /> Information submitted by the Discharger indicate that the effluent contains trihalomethanes(THMs) River at Vernalis and the average discharge flow. However,the Regional Board finds that granting of
<br /> including chloroform. The Basin Plan contains the"Chemical Constituent"objective that requires,at a this dilution credit would allocate an unnecessarily large portion of the River's assimilative capacity
<br /> minimum,that waters with a designated MUN use not exceed California MCLS. In addition,the for these constituents and could violate the Antidegradation Policy. Instead,effluent limitations have
<br /> Chemical Constituent objective prohibits chemical constituents in concentrations that adversely affect been developed based on the amount of dilution that would be required,such that receiving water
<br /> beneficial uses. The California's Drinking Water Standard primary MCL for total THMs is 100 ug/1. concentrations for these constituents would be met when effluent concentrations are at estimated
<br /> The USEPA primary MCL for total THMs is 80 ug/1,which was effective on 1 January 2002 for maximum levels as determined by taking the mean plus 3.3-standard deviations or the maximum
<br /> surface water systems that serve more than 10,000 people. Pursuant to the Safe Drinking Water Act, observed concentration,which ever is larger,for data sets with 10 or more values. For data sets with
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